//
// crypt.c
//
// DES based implementation of crypt()
//
// Copyright (C) 2005 Michael Ringgaard. All rights reserved.
// Copyright (C) 1999 America Online, Inc. All Rights Reserved.
//
// The contents of this file are subject to the AOLserver Public License
// Version 1.1 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at
// http://aolserver.com/.
//
// Software distributed under the License is distributed on an "ZHIA IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
// the License for the specific language governing rights and limitations
// under the License.
//
// The Original Code is AOLserver Code and related documentation
// distributed by AOL.
// 
// The Initial Developer of the Original Code is America Online, Inc. 
// Portions created by AOL are Copyright (C) 1999 America Online,Inc. 
// All Rights Reserved.
//

#include <sys/types.h>

//
// This program implements the Proposed Federal Information Processing Data
// Encryption Standard. See Federal Register, March 17, 1975 (40FR12134)
//

//
// Initial permutation
//

static const char IP[] = {
  58, 50, 42, 34, 26, 18, 10, 2,
  60, 52, 44, 36, 28, 20, 12, 4,
  62, 54, 46, 38, 30, 22, 14, 6,
  64, 56, 48, 40, 32, 24, 16, 8,
  57, 49, 41, 33, 25, 17, 9, 1,
  59, 51, 43, 35, 27, 19, 11, 3,
  61, 53, 45, 37, 29, 21, 13, 5,
  63, 55, 47, 39, 31, 23, 15, 7,
};

//
// Final permutation, FP = IP^(-1)
//

static const char FP[] = {
  40, 8, 48, 16, 56, 24, 64, 32,
  39, 7, 47, 15, 55, 23, 63, 31,
  38, 6, 46, 14, 54, 22, 62, 30,
  37, 5, 45, 13, 53, 21, 61, 29,
  36, 4, 44, 12, 52, 20, 60, 28,
  35, 3, 43, 11, 51, 19, 59, 27,
  34, 2, 42, 10, 50, 18, 58, 26,
  33, 1, 41, 9, 49, 17, 57, 25,
};

//
// Permuted-choice 1 from the key bits to yield C and D. Note that bits
// 8,16... are left out: They are intended for a parity check.
//

static const char PC1_C[] = {
  57, 49, 41, 33, 25, 17, 9,
  1, 58, 50, 42, 34, 26, 18,
  10, 2, 59, 51, 43, 35, 27,
  19, 11, 3, 60, 52, 44, 36,
};

static const char PC1_D[] = {
  63, 55, 47, 39, 31, 23, 15,
  7, 62, 54, 46, 38, 30, 22,
  14, 6, 61, 53, 45, 37, 29,
  21, 13, 5, 28, 20, 12, 4,
};

//
// Sequence of shifts used for the key schedule.
//

static const char shifts[] = {
  1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1,
};

//
// Permuted-choice 2, to pick out the bits from the CD array that generate
// the key schedule.
//

static const char PC2_C[] = {
  14, 17, 11, 24, 1, 5,
  3, 28, 15, 6, 21, 10,
  23, 19, 12, 4, 26, 8,
  16, 7, 27, 20, 13, 2,
};

static const char PC2_D[] = {
  41, 52, 31, 37, 47, 55,
  30, 40, 51, 45, 33, 48,
  44, 49, 39, 56, 34, 53,
  46, 42, 50, 36, 29, 32,
};

//
// The following structure maitains the key schedule.
//

struct sched {
  // The C and D arrays used to calculate the key schedule.
  char C[28];
  char D[28];

  // The key schedule. Generated from the key.
  char KS[16][48];

  // The E bit-selection table.
  char E[48];
};

static const char e[] = {
  32, 1, 2, 3, 4, 5,
  4, 5, 6, 7, 8, 9,
  8, 9, 10, 11, 12, 13,
  12, 13, 14, 15, 16, 17,
  16, 17, 18, 19, 20, 21,
  20, 21, 22, 23, 24, 25,
  24, 25, 26, 27, 28, 29,
  28, 29, 30, 31, 32, 1,
};

//
// Set up the key schedule from the key.
//

static void setkey_r(struct sched *sp, const char *key) {
  int i, j, k;
  int t;

  // First, generate C and D by permuting the key.  The low order bit of
  // each 8-bit char is not used, so C and D are only 28 bits apiece.
  for (i = 0; i < 28; i++) {
    sp->C[i] = key[PC1_C[i] - 1];
    sp->D[i] = key[PC1_D[i] - 1];
  }

  // To generate Ki, rotate C and D according to schedule and pick up a
  // permutation using PC2.
  for (i = 0; i < 16; i++) {
    // Rotate
    for (k = 0; k < shifts[i]; k++) {
      t = sp->C[0];
      for (j = 0; j < 28 - 1; j++) sp->C[j] = sp->C[j + 1];
      sp->C[27] = t;
      t = sp->D[0];
      for (j = 0; j < 28 - 1; j++) sp->D[j] = sp->D[j + 1];
      sp->D[27] = t;
    }

    // Get Ki (note C and D are concatenated)
    for (j = 0; j < 24; j++) {
      sp->KS[i][j] = sp->C[PC2_C[j] - 1];
      sp->KS[i][j + 24] = sp->D[PC2_D[j] - 28 - 1];
    }
  }

  for (i = 0; i < 48; i++) sp->E[i] = e[i];
}

//
// The 8 selection functions. For some reason, they give a 0-origin index,
// unlike everything else.
//

static const char S[8][64] = {
  { 14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
     0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
     4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
    15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13 },

  { 15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
     3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
     0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
    13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9 },

  { 10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
    13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
    13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
     1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12 },

  {  7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
    13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
    10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
     3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14 },

  {  2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
    14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
     4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
    11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3 },

  { 12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
    10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
     9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
     4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13 },

  {  4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
    13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
     1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
     6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12 },

  { 13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
     1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
     7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
     2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11 },
};

//
// P is a permutation on the selected combination of the current L and key
//

static const char P[] = {
  16, 7, 20, 21,
  29, 12, 28, 17,
  1, 15, 23, 26,
  5, 18, 31, 10,
  2, 8, 24, 14,
  32, 27, 3, 9,
  19, 13, 30, 6,
  22, 11, 4, 25,
};

//
// Encrypt a block
//

static void encrypt_r(struct sched *sp, char *block, int edflag) {
  // The current block, divided into 2 halves.
  char L[64], *R = L + 32;
  char tempL[32];
  char f[32];

  // The combination of the key and the input, before selection
  char preS[48];

  int i, ii;
  int t, j, k;

  // First, permute the bits in the input
  for (j = 0; j < 64; j++) L[j] = block[IP[j] - 1];

  // Perform an encryption operation 16 times
  for (ii = 0; ii < 16; ii++) {
    // Set direction
    if (edflag) {
      i = 15 - ii;
    } else {
      i = ii;
    }

    // Save the R array, which will be the new L
    for (j = 0; j < 32; j++) tempL[j] = R[j];

    // Expand R to 48 bits using the E selector; exclusive-or with the current key bits
    for (j = 0; j < 48; j++) preS[j] = R[sp->E[j] - 1] ^ sp->KS[i][j];

    // The pre-select bits are now considered in 8 groups of 6 bits each.
    // The 8 selection functions map these 6-bit quantities into 4-bit
    // quantities and the results permuted to make an f(R, K). The
    // indexing into the selection functions is peculiar; it could be
    // simplified by rewriting the tables.

    for (j = 0; j < 8; j++) {
      t = 6 * j;
      k = S[j][(preS[t + 0] << 5) +
          (preS[t + 1] << 3) +
          (preS[t + 2] << 2) +
          (preS[t + 3] << 1) +
          (preS[t + 4] << 0) +
          (preS[t + 5] << 4)];
      t = 4 * j;
      f[t + 0] = (k >> 3) & 01;
      f[t + 1] = (k >> 2) & 01;
      f[t + 2] = (k >> 1) & 01;
      f[t + 3] = (k >> 0) & 01;
    }

    // The new R is L ^ f(R, K). The f here has to be permuted first, though.
    for (j = 0; j < 32; j++) R[j] = L[j] ^ f[P[j] - 1];

    // Finally, the new L (the original R) is copied back.
    for (j = 0; j < 32; j++) L[j] = tempL[j];
  }

  // The output L and R are reversed.
  for (j = 0; j < 32; j++) {
    t = L[j];
    L[j] = R[j];
    R[j] = t;
  }

  // The final output gets the inverse permutation of the very original.
  for (j = 0; j < 64; j++) block[j] = L[FP[j] - 1];
}

osapi char *crypt_r(const char *key, const char *salt, char *buf) {
  int i, j, c;
  int temp;
  char block[66];
  struct sched s;

  for (i = 0; i < 66; i++) block[i] = 0;
  for (i = 0; (c = *key) && i < 64; key++) {
    for (j = 0; j < 7; j++, i++) block[i] = (c >> (6 - j)) & 01;
    i++;
  }

  setkey_r(&s, block);

  for (i = 0; i < 66; i++) block[i] = 0;

  for (i = 0; i < 2; i++) {
    c = *salt++;
    buf[i] = c;
    if (c > 'Z') c -= 6;
    if (c > '9') c -= 7;
    c -= '.';
    for (j = 0; j < 6; j++) {
      if ((c >> j) & 01) {
        temp = s.E[6 * i + j];
        s.E[6 * i + j] = s.E[6 * i + j + 24];
        s.E[6 * i + j + 24] = temp;
      }
    }
  }

  for (i = 0; i < 25; i++) encrypt_r(&s, block, 0);

  for (i = 0; i < 11; i++) {
    c = 0;
    for (j = 0; j < 6; j++) {
      c <<= 1;
      c |= block[6 * i + j];
    }
    c += '.';
    if (c > '9') c += 7;
    if (c > 'Z') c += 6;
    buf[i + 2] = c;
  }
  buf[i + 2] = 0;
  if (buf[1] == 0) buf[1] = buf[0];

  return buf;
}
